The Tissue Level of Organization

Learning Objectives Identify the four major tissue types and describe their functions. Describe the relationship between form and function for each tissue type. Discuss the types and functions of epithelial tissues. Compare the structure and function of connective tissues.

Learning Objectives Explain the structure and function of the four types of membrane. Describe the three types of muscle tissue and the structural features of each. Discuss the basic structure and role of neural tissue.

SECTION 4-1 Tissues of the Body: An Introduction

Tissues and tissue types Tissues are: Collections of specialized cells and cell products organized to perform a limited number of functions Histology = study of tissues The four tissue types are: Epithelial Connective Muscular Nervous

Epithelial tissue Includes glands and epithelium Glands are secretory Is avascular Forms a protective barrier that regulates permeability Cells may show polarity

Functions of epithelium Physical protection Control permeability Provide sensation Produce specialized secretions

Specializations of epithelium Perform secretory functions Perform transport functions Maintain physical integrity Ciliated epithelia move materials across their surface

Figure 4.1 The Polarity of Epithelial Cells

Maintaining the integrity of epithelium Cells attach via cell adhesion molecules (CAM) Cells attach at specialized cell junctions Tight junctions Desmosomes Gap junctions

Figure 4.2 Intercellular connections PLAY Animation: Intercellular connections Figure 4.2

Structure of typical epithelium Basal lamina attaches to underlying surface Lamina lucida Lamina densa Germinative cells replace short-lived epithelial cells

Classification of epithelia Number of cell layers Simple Stratified Shape of apical surface cells Squamous Cuboidal Columnar

Figure 4.3 Squamous Epithelia

Figure 4.4 Cuboidal Epithelia Figure 4.4a

Figure 4.4 Cuboidal Epithelia Figure 4.4b

Figure 4.4 Transitional Epithelium Figure 4.4c

Figure 4.5 Columnar Epithelia Figure 4.5a

Figure 4.5 Columnar Epithelia Figure 4.5b

Figure 4.5 Columnar Epithelia

Glandular epithelia Exocrine glands Secrete through ducts onto the surface of the gland Endocrine glands Release hormones into surrounding fluid

Glandular secretions can be: Merocrine (product released through exocytosis) Apocrine (involves the loss of both product and cytoplasm) Holocrine (destroys the cell)

Figure 4.6 Mechanisms of Glandular Secretion PLAY Animation: Mechanisms of glandular secretion Figure 4.6

Glands Unicellular Individual secretory cells Multicellular Organs containing glandular epithelium Classified according to structure

Figure 4.7 A Structural Classification of Exocrine Glands

SECTION 4-3 Connective Tissues

Connective tissue functions: Establishing a structural framework Transporting fluids and dissolved materials Protecting delicate organs Supporting, surrounding and interconnecting tissues Storing energy reserves Defending the body from microorganisms

Figure 4.8 A Classification of Connective Tissues

Connective tissues contain Specialized cells Matrix Composed of extracellular protein fibers and a ground substance

Connective tissue proper Contains varied cell populations Contains various fiber types A syrupy ground substance

Fluid connective tissue Contains a distinctive cell population Watery ground substance with dissolved proteins Two types Blood Lymph

Supporting connective tissues Less diverse cell population Dense ground substance Closely packed fibers Two types Cartilage Bone

Connective tissue proper Contains fibers, a viscous ground substance, and a varied cell population Fibroblasts Macrophage Adipocytes Mesenchymal cells Melanocytes Mast cells Lymphocytes Microphages

Connective tissue proper Three types of fiber Collagen fibers Reticular fibers Elastic fibers

Connective tissue proper Classified as loose or dense Loose Embryonic mesenchyme, mucous connective tissues Areolar tissue Adipose tissue Reticular tissue Dense Dense regular CT Dense irregular CT

Figure 4.9 The Cells and Fibers of Connective Tissue Proper

Figure 4.10 Connective Tissue in Embryos

Figure 4.11 Adipose and Reticular Tissues

Figure 4.12 Dense Connective Tissues Figure 4.12a

Figure 4.12 Dense Connective Tissues Figure 4.12b

Figure 4.12 Dense Connective Tissues Figure 4.12c

Fluid connective tissues Distinctive collections of cells in a fluid matrix Blood Formed elements and plasma Red blood cells, white blood cells and platelets Arteries carry blood away, veins carry to the heart Capillaries allow diffusion into the interstitial fluid Lymph Interstitial fluid entering the lymphatic vessels

Figure 4.13 Formed Elements of the Blood

Supporting connective tissues Cartilage and bone support the rest of the body Cartilage Grows via interstitial and appositional growth Matrix is a firm gel containing chondroitin sulfate Cells called chondrocytes Cells found in lacunae Perichondrium separates cartilage from surrounding tissues Three types: hyaline, elastic and fibrocartilage

Figure 4.15 The Perichondrium and Types of Cartilage Figure 4.15a, b

Figure 4.15 The Perichondrium and Types of Cartilage Figure 4.15c

Figure 4.15 The Perichondrium and Types of Cartilage Figure 4.15d

Bone, or osseus tissue Has osteocytes Depend on diffusion through canaliculi for nutrients Little ground substance Dense mineralized matrix Surrounded by periosteum

Figure 4.16 Bone Figure 4.16

SECTION 4-4 Membranes

Membranes are simple organs Form a barrier Composed of epithelium and connective tissue Four types Cutaneous Synovial Serous Mucous

Figure 4.17 Membranes Figure 4.17a-d

Mucous membranes Line cavities that communicate with the exterior Contain lamina propria

Serous membranes Line sealed internal cavities Form transudate

Cutaneous membrane Covers the body surface Synovial membrane Incomplete lining within joint cavities

SECTION 4-5 The Connective Tissue Framework of the Body

Organs and systems are interconnected Network of connective tissue proper consisting of Superficial fascia Deep fascia Subserous fascia

Figure 4.18 The Fasciae Figure 4.18

SECTION 4-6 Muscle Tissue

Muscle tissue Specialized for contraction Three types Skeletal Cardiac Smooth

Figure 4.19 Muscle Tissue Figure 4.19a

Figure 4.19 Muscle Tissue Figure 4.19b

Figure 4.19 Muscle Tissue Figure 4.19c

Skeletal muscle Cells are multinucleate Striated voluntary muscle Divides via satellite cells

Cardiac muscle Cardiocytes occur only in the heart Striated involuntary muscle Relies on pacemaker cells for regular contraction

Smooth muscle tissue Non-striated involuntary muscle Can divide and regenerate

SECTION 4-7 Neural Tissue

Neural tissue Conducts electrical impulses Conveys information from one area to another

Neural tissue cells Neurons Transmit information Neuroglia Support neural tissue Help supply nutrients to neurons

Figure 4.20 Neural Tissue Figure 4.20

Neural anatomy Cell body Dendrites Axon (nerve fiber) Carries information to other neurons

SECTION 4-8 Tissue Injuries and Aging

Inflammation and regeneration Injured tissues respond in coordinated fashion Homeostasis restored by inflammation and regeneration

Inflammatory response Isolates injured area Damaged cells, tissue components and dangerous microorganisms removed Infection avoided Regeneration restores normal function

Figure 4.21 An Introduction to Inflammation

Aging and tissue repair Change with age Repair and maintenance less efficient Structure altered Chemical composition altered

Aging and cancer incidence Incidence of cancer increases with age 70-80% of all cases due to exposure to chemicals or environmental factors

Figure 4.22 Changes in a Tissue under Stress

You should now be familiar with: The four major tissue types and their functions. The relationship between form and function for each tissue type. The types and functions of epithelial tissues. The structure and function of connective tissues. The structure and function of the four types of membrane. The three types of muscle tissue and the structural features of each. The basic structure and role of neural tissue.